A026372 a(n) = greatest k such that s(k) = n, where s = A026370.

4, 7, 10, 15, 18, 23, 26, 31, 34, 37, 40, 45, 48, 53, 56, 59, 62, 67, 70, 75, 78, 81, 84, 89, 92, 97, 100, 105, 108, 113, 116, 119, 122, 127, 130, 135, 138, 141, 144, 149, 152, 157, 160, 165, 168, 173, 176, 179, 182, 187, 190, 195, 198